Problem: $ { \left[\begin{array}{r}{2} \\ {4} \\ {-1}\end{array}\right]+\left[\begin{array}{r}{0} \\ {-1} \\ {-2}\end{array}\right] = {?} } $
Explanation: To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{r}{2}+{0} \\ {4}+{-1} \\ {-1}+{-2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{r}{2} \\ {3} \\ {-3}\end{array}\right]}$